A coupled field‐scale aquifer pumping and water infiltration test was conducted at the Idaho National Engineering and Environmental Laboratory in order to evaluate subsurface water and contaminant transport processes in a heterogeneous flow system. The test included an aquifer pumping test to determine the storage properties of the aquifer and the state of confinement of the aquifer (∼190 m below land surface), and a vadose zone infiltration test to determine vertical moisture and radioactive tracer migration rates. Pump test results indicated that the Snake River Plain Aquifer was locally unconfined with a transmissivity ranging from 5.57 × 105 to 9.29 × 104 m2day. Moisture monitoring with neutron probes indicated that infiltrating water was initially transported vertically through the upper basalt layer of the vadose zone, primarily through fractures and rubble zones, at an average rate of 5 m/day (based on vertical distance traveled and first arrival of water at the monitoring points). Analysis of breakthrough curves for a conservative tracer allowed estimation of the arrival of the peak concentration and yielded an average velocity of 1 m/day. The migration velocities from the neutron probe and tracer tests are in good agreement given the scale of the test and difference in analysis techniques. None of the data sets showed a correlation between migration velocity (arrival time) and distance from the point source, but they strongly indicate preferential flow through discrete fractures. Upon reaching the first continuous sedimentary interbed layer in the basalt formation, water flow was diverted laterally along the interbed surface where it spread outward in primarily three areas corresponding to topographic lows on the interbed surface, and slowly infiltrated into the interbed. The nonpredictable movement of water and tracer through specific fractures underlying the site suggests that a priori prediction of trans‐missive fractures in this media is not possible. Results do suggest that the continuous sedimentary interbed layers, in general, impede vertical water flow and contaminant migration.

Waste disposal sites with volatile organic compounds (VOCs) frequently contain contaminants that are present in both the ground water and vadose zone. Vertical sampling is useful where transport of VOCs in the vadose zone may effect ground water and where steep vertical gradients in chemical concentrations are anticipated. Designs for combination ground water and gas sampling wells place the tubing inside the casing with the sample port penetrating the casing for sampling. This physically interferes with pump or sampler placement. This paper describes a well design that combines a ground water well with gas sampling ports by attaching the gas sampling tubing and ports to the exterior of the casing. Placement of the tubing on the exterior of the casing allows exact definition of gas port depth, reduces physical interference between the various monitoring equipment, and allows simultaneous remediation and monitoring in a single well. The usefulness and versatility of this design was demonstrated at the Idaho National Engineering and Environmental Laboratory (INEEL) with the installation of seven wells with 53 gas ports, in a geologic formation consisting of deep basalt with sedimentary interbeds at depths from 7.2 to 178 m below land surface. The INEEL combination well design is easy to construct, install, and operate.